In the field of wireless communications, and particularly wireless cellular communications, there has been increasing interest in recent years in the idea of moving more of the signal processing functions of the transceiver into software. A transceiver with a tendency towards software implementation is sometimes referred to as a software modem, or “soft modem”. The principle behind software modem is to perform a significant portion of the signal processing required for the wireless communications in a generic, programmable, reconfigurable processor, rather than in dedicated hardware.
An advantage of a soft modem type system is that it can be programmed and potentially reprogrammed to handle different protocols, algorithms, functions, radio access technologies and the like. For example, conventionally different radio access technologies would require different dedicated hardware to be included on a phone or other wireless terminal, and a terminal adapted to handle multiple radio access technologies or “multimode” terminal would have to include different sets of dedicated hardware. This problem is solved by software modem techniques, in which the differences in communicating according to different radio access technologies are handled in software. The processor could be programmed to handle both 2G and 3G cellular standards, including for example perhaps one or more of the GSM, UMTS, EDGE, DigRF, High Speed Downlink Packet Access (HSDPA), and High Speed Uplink Packet Access (HSUPA), and 3GPP Long Term Evolution (LTE) standards.
Alternatively or additionally, the use of software modem techniques may allow a manufacturer, distributor or vendor to buy a batch of generic or “standard agnostic” processors and then program them according to different radio standards and technologies for different customers or purposes. A soft modem could also be updated easily and inexpensively by reprogramming it to handle new or different technologies.
However, the difficulty in implementing a soft modem in practice is that, for a given processor, there may not be sufficient processing resources available to be able to provide as high a performance as would be preferred. This is especially likely to be the case in a relatively low cost consumer device such as a mobile phone. However, it would nonetheless be desirable that the soft modem's performance should be of a level that would be competitive with its hardware counterparts. In other cases, the constraint on the use of processing resources may not be set by the limit of the computational capabilities of the processor, but by the requirement to limit the power consumption of the device in general or under specific modes or operating conditions.